Theoretical study of molecular properties of low-lying electronic excited states of H2O and H2S |
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Authors: | Jana Páleníková Michal Kraus Pavel Neogrády Miroslav Urban |
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Institution: | Faculty of Natural Sciences, Department of Physical and Theoretical Chemistry , Comenius University , Bratislava, Slovakia |
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Abstract: | Geometries, excitation energies, dipole moments and dipole polarisability tensor components of the ground and four lowest excited states 3 B 1, 1 B 1, 3 A 2, 1 A 2 of the H2O and H2S molecules were calculated at the CASSCF, CASPT2, CCSD and CCSD(T) level of approximation. Vertical excitation and equilibrium transition energies of these states, having the Rydberg character, are reported too. Properties of both molecules in the ground and in low lying excited states are compared and discussed from the point of view of their molecular electronic structure. Upon excitation we observe dramatic changes of dipole moments and polarisabilities with respect to the ground state. We stress the change of the polarity of H2O in all excited states accompanied by the enhancement of the dipole polarisability by an order of magnitude. Large, even if less pronounced, are changes of electric properties of H2S in its excited states. Dipole moments and dipole polarisabilities of 3 B 1, 1 B 1 states of H2S and H2O behave quite analogously in comparison to their respective ground state. The general pattern of properties for both molecules in their 3 A 2 and 1 A 2 excited states is more different due to a pronounced participation of the sulphur d-orbitals in these states of the H2S molecule. |
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Keywords: | excited states Rydberg states H2O H2S excitation energies dipole moment dipole polarisability CASPT2 CCSD(T) |
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